Studies are proposed to determine some of the important factors involved in the control of pepsinogen release. The studies will be focused primarily on isolated pepsinogen granules. Attempts will be made to purify these granules and to study the effects of cyclic nucleotides on the release of pepsinogen from them. In addition other factors influencing pepsinogen release will be investigated. In particular it will be of interest to determine if protein phosphorylation is involved in these processes. Another facet of the proposed investigation concerns the characterization of the guanyl and adenyl cyclase enzyme systems of the gastric mucosa, to determine if regulation of these enzyme systems by gastric secretagogues can be demonstrated.